Trimmer Head Spool Asymmetric Teeth Counterweight Vibration
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Solution Overview
Problem
String trimmers experience significant vibration due to eccentric forces caused by imbalances during high-speed rotation, which reduces their service life and increases the strength requirements of components.
Innovation Solution
The trimmer head design incorporates a spool with first transmission teeth and a head housing with second transmission teeth, where the second transmission teeth are biased to offset the eccentric force, allowing the force to be composed of component forces that drive synchronous rotation, reducing vibration and material requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor drives the trimmer head to rotate at high speed, then the cutting function is improved, but the vibration increases and harms the strength of the string trimmer
Solution Approach 1:
The patent applies counterweight principle by designing the spool with an asymmetric structure where the center of gravity is offset from the rotation axis. A counterweight portion is added to balance the eccentric force generated during high-speed rotation, thereby reducing vibration and protecting the strength of the string trimmer while maintaining effective cutting performance
2Force
If the transmission teeth are designed to engage firmly, then the force transmission is improved, but the vibration between spool and head housing increases
Solution Approach 1:
The counterweight portion on the spool generates an eccentric force that opposes the vibration force produced during engagement of transmission teeth. This balance mechanism reduces the net vibration between spool and head housing while preserving effective force transmission for driving the trimmer line
Solution Approach 2:
The transmission teeth are designed with asymmetric engagement characteristics where the pushing force and returning force have different paths and magnitudes. This asymmetric design, combined with the counterweight, allows firm force transmission during the power stroke while minimizing vibration during the return stroke
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces vibration between the spool and head housing, lowering the structural strength requirements and extending the service life of the trimmer head.
Implementation Method 1
the plurality of first transmission teeth engage with the plurality of second transmission teeth to transmit force between the head housing and the spool
Implementation Method 2
the force has a first component force along the first direction and a second component force along the second direction to drive one of the head housing and the spool to rotate with the other
Data Source
AI summary
A trimmer head includes a spool configured to rotate about a rotation axis. The spool is provided with a plurality of first transmission teeth. A head housing accommodates at least a part of the spool. The head housing is provided with a plurality of second transmission teeth for engaging with the plurality of first transmission teeth. When the trimmer head rotates about the rotation axis and along a predetermined direction, the plurality of first transmission teeth engage with the plurality of second transmission teeth to transmit force between the head housing and the spool. The force acts on a point of action of the head housing or the spool to drive the head housing and the spool to rotate synchronously along the predetermined direction.